1. Field of the Invention
The present invention relates to a resin composition with excellent molding properties, mechanical strength, impact resistance and the like. More particularly, the present invention relates to a resin composition comprising (A) a polyphenylene ether resin, (B) a polyolefin resin and (C) a graft modified copolymer modified with a specified monomer which is capable of radical graft polymerization under the conditions of radical graft polymerization. The composition provides molding articles which satisfy highly required performance of structural components and the like of automobiles and electrical equipment, in which heat resistance and mechanical strength characteristic of polyphenylene ether resins, and molding properties and resistance to organic solvents characteristic of polyolefin resins are not greatly reduced, with their impact resistance being improved remarkably.
2. Discussion of the Background
It is well known that a polyphenylene ether resin consisting of ring-unsubstituted or ring-substituted phenylene groups, particularly poly-2,6-dimethyl-1,4-phenylene ether, which is excellent in heat resistance and mechanical strength, is useful for engineering resins. For use as a molding material, however, the polyphenylene ether resin-has poor stability for injection molding, extrusion molding and the like. Further, polyphenylene ether resins has poor impact resistance, solvent resistance for engineering resins in a variety of application fields.
There is a well-known idea that an approach to blending other resin materials compensates for insufficient properties when a single resin material does not enough satisfy various desired properties. Materials of polyphenylene ether having improved molding properties by compounding polystyrene are widely provided for practical use, which has suitable molding properties and compatibility with polyphenylene ether. In this case, both components have poor resistance to organic solvents and thus the blended composition should be insufficient for solvent resistance. On the other hand, a polyolefin resin which is inexpensive as well as excellent in molding properties, resistance to organic solvents and the like has been used as materials for molded objects, but does not meet the needs of engineering resins, because its heat resistance is not high enough.
If a composition which combines the good properties of a polyphenylene ether resin and a polyolefin resin together is obtained, an excellent resin material having a wide application field can be provided.
However, as can be understood from a thermodynamic discussion of a general polymer blends, polyphenylene ether is incompatible with polyolefin and there is no affinity between the former and the latter. Therefore, a composition blended with only two components has poor adhesion properties in the boundary of the two-phase structure, so that the boundary of two-phase of molded objects obtained will become defective parts having low strength and will tend to reduce the mechanical strength and impact resistance. The boundary part is easily delaminated when subjected to shearing stress during the molding process such as injection molding and the like.
Generally, one of the possible approaches to resolve the above mentioned problems in an incompatible polymer blend is blending a third component to improve affinity of the desired two-component composition.
A material referred to as a compatibilizing agent is the representative third component. It is ideal that a compatibilizing agent is laid in the interface of the first component and the second component, exhibits affinity to the both components, improves the poor adhesion properties, and leads to be capable of making more homogeneous dispersion structure. For example, Japanese Patent Laid-Open No. 58-103557 describes that a block or radical tereblock copolymer of an alkenyl aromatic compound and a conjugated diene acts as "a compatibility imparting agent", and that polyolefin is blended homogeneously with polyphenylene ether in an appropriate ratio. Japanese Patent Publication No. 56-22344 describes a method for preventing reduction of mechanical strength of unmodified polypropyrene to be used by compounding modified polypropyrene, i.e., polypropyrene modified with a styrene monomer and an organic peroxide to polyphenylene ether. When large amount of polyphenylene ether and large amount of unmodified polypropyrene, however, are compounded, the use of such a conventional compatibility imparting agent does not lead to satisfactory results as an affinity modifying agent.
The present invention provides a resin composition which is excellent in heat resistance, solvent resistance and molding properties, and which has high impact resistance.